Well treating methods using temperature surveys



F PMH Nov. 25, 1969 J. H. GUINN ET AL 3,480,079

WELL TREATING METHODS USING TEMPERATURE SURVEYS 2 Sheets-Sheet 1 FiledJune 7,

INVENTORS m m N a. m m M v m A GS Hm Wm w a r" aw Y B Nov. 25, 1969 J.H. GUINN ET AL 3,480,079

WELL TREATING METHODS USING TEMPERATURE SURVEYS Filed Junev 7, 1968 2Sheets-Sheet 2 INVE NTORS Jerry H. Gumn n E .fl s m M W United StatesPatent 3,480,079 WELL TREATING METHODS USING TEMPERATURE SURVEYS JerryI-I. Guinn, Amarillo, and William Sherwood Wright, Midland, Tex.,assignors of fifty percent to Cardinal Chemical, Inc., Odessa, Tex., andProducers Chemical Company, Amarillo, Tex., both corporations of TexasFiled June 7, 1968, Ser. No. 735,313 Int. Cl. E21b 47/00, 43/24, 43/20US. Cl. 166-250 18 Claims ABSTRACT OF THE DISCLOSURE A method oftreating wells to stimulate production from or to increase acceptance offluids in the well strata by controlled selective treatment of theformations of the well in conjunction with temperature evaluation.Blocking and propping agents are utilized to block off each zone orstrata as it is treated. Temperature gradient curves and temperaturedifferential curves are utilized This invention relates to the method oftreating wells to stimulate production from or injection into the wellstrata, and the process and material used in connection therewith.

It is an important object of the invention to provide an improved methodfor treating wells utilizing downhole temperature logging equipment torecord the temperature gradient and the temperature differentials in thewell bore to trace the entry of treating fluids into formations beingtreated and to determine the extent of entry of such fluids intoproductive sections or adjacent areas, and to use the informationobtained by such logging equipment to design the stages of treatment ofthe well and to select materials to be used in effecting such treatment.

Another object of the invention is to provide a process by means ofwhich the movement of fluids into or out of selected zones of a wellbore drilled through subsurface strata of varying zones of permeabilityand porosity.

A further object of the invention is to provide means for achievingproper down-hole diversion of the various stages of a multistagestimulation treatment, such as acidizing and/ or hydraulic fracturing,temporary or permanent squeezing of treating fluids into the wellformations to effect the desired movement of fluids into or out of andto control such movement of fluids into or out of selected zones in thewell bore.

A further object of the invention is to provide a system and materialsfor utilization in effecting the treatment of the wells as hereinaboveset forth.

Additional objects and advantages of the invention will be readilyapparent from the reading of the following description of the method,system and materials utilized in accordance with the invention andreference to the accompanying drawings, wherein:

FIGURE 1 is a schematic view of a well bore having alongside atemperature log representing the temperature gradient curve and thetemperature differential curve for the well bore indicated;

FIGURE 2 is a view similar to FIGURE 1 showing a 3,480,079 Patented Nov.25, 1969 treatment of the well in accordance with the invention in thesecond from upper Zone or strata of the well;

FIGURE 3 is a view similar to FIGURE 2 showing the second zone blockedand the third zone undergoing treatment;

FIGURE 4 is a view similar to FIGURE 3 illustrating the third stage oftreatment wherein the second and third zones are blocked and the upperzone is undergoing treatment; and,

FIGURE 5 is a view similar to FIGURE 4 showing the upper three zonesblocked and treatment being effected in the lowest of the zones.

Long open hole, or heavily perforated intervals, with zones or strata ofvarying porosities and permeabilities have always been difficultstimulation problems. Continuous treatment processes heretofore usedwith various types of blocking agents or diverting agents have notpermitted any evaluation of the treatment being effected, because onlyafter the complete process had been accomplished could any down-holeevaluation of the success of the diverting agents and the treatingagents be estimated. As a result, critical information such as theextent of the formation treated per stage, communicating zones,channeling behind the casing, and other information was unavailableuntil after the treatment had been completed. This invention has to dowith the method of treating wells wherein a temperature survey iseffected immediately after each stage of treatment of the well toprovide for an immediately evaluation of the results of the treatmentand to provide information from which additional stages of treatment maybe designed and effected. As each stage is carried out by pumping thetreating fluids into the well, it is in turn evaluated by a temperaturesurvey, and the proper amount of treating fluids or materials iscalculated for the subsequent treating stages.

For example, in the Permian Basin and Anadarko Basin, many of the wellshave been drilled long previously and have large open holes below thecasing string, long sections and numerous zones of varying porositiesand permeabilities; or, have been shot with nitroglycerin or the like tofracture the formation to increase production, and sometimes treatedwith acid or other treating fluids. Later wells have had long strings ofperforations shot through casing which had been set through the paysections, and more recent completions have had a limited number ofperforations through the casing extending over a considerable distancein the well bore, or located at several different intervals in the wellbore.

As a result, wells of these types usually have one or more of thefollowing conditions present: zones with different bottom hole trea ingpressures, communication or intercommunication between zones, intervalstoo long to be successfully stimulated in one stage, channeling betweenzones or behind the casing, thief zones and other conditions whichprevent successful treatment of all zones by the continuous multistagestimulation method. Such formerly used process involved the treatment ofthe well without the cessation of pumping by introducing a firststimulation stage, such as acid, water, oil, and so forth; theintroduction of a predetermined amount of diverting or blockingmaterial; the pumping of the next stimulation stage; the introduction ofanother diversion or blocking stage; and the continuance of this processuntil all stimulation stages calculated to be necessary were pumped intothe well in an attempt to effect treatment of all zones; and continueduntil all zones of fluid entry into the well bore or from the well borewere sealed. At no time during this operation was the process stoppedand down-hole evaluation made as to the success of the various diversionand treatment stages, so that the success of the operation wascontingent upon arbitrary estimation of the proper volumes of treatingmaterials and diverting materials to be introduced.

The method of this invention consists in running a temperature loggingtool, such as that made and sold by Radiation Engineering andManufacturing Company of Fort Worth, Tex., by means of which a plot oftemperature against depth is effected. In addition, the temperaturegradient curve obtained as a result of the recording of the temperaturechange due to the bore passing through the various earth formations, atemperature differential curve is recorded simultaneously by such devicewhich indicates changes in that temperature, showing the temperaturedifferential obtained by recording continuously and instantaneously thefirst derivative of the gradient log by making measurements a slightvertical distance apart, storing or delaying the original measurementwith a memory system in the tool, or delay system in the tool, and thenrecording such first derivative of the change as the tool progressesthrough the well bore.

This temperature logging tool is a commercially available tool anditself forms no part of this invention. However, the method of utilizingthe tool is an essential part of the invention.

In carrying out the invention, the first step is the running of a basetemperature log for the well. This log is run prior to starting anystimulation or treatment of the well. The log so obtained points out anydown-hole temperature anomalies present in the well prior to treating,and so provides a means for better interpretation of subsequent logs.The schematic illustration of FIGURE 1 indicates a well bore 10 having acasing 11 with a show 12 at the lower end thereof, and an open hole .13below the casing. Producing formations 21, 22, 23 and 24 are illustratedschematically at one side of the illustration of the open hole. To theright of the well bore illustration is a schematic illustration of atemperature log obtained from a temperature survey taken prior totreatment of the well. The absolute or temperature gradient log curve isindicated by the numeral 50, the increase in temperature being indicatedby the slope of the curve to the right. The temperature differentialcurve is indicated at 60 and indicates by deviations from the verticalthe changes in the temperature between closely adjacent areas in thewell bore. After the first base log has been obtained, a first stage ofstimulation of the well is introduced in the usual manner by pumpingfrom the well surface treating fluid, which may be an acid fracturingfluid, water, or oil, or the like, introduced into the well bore andpumped in the usual manner into one of the zones in the well. Thetreating fluid introduced into the well may be intentionally initiallyheated or cooled, if necessary, to provide a temperature diiferentialbetween the ambient or formation temperature and the temperature of thetreating fluid. It is desirable that at least a ten degree F. differencebetween the ambient surface temperature of the treating fluid and thebottom hole temperature of the formations to be treated exist. Whetherthe fluid is 10 degrees F. hotter or 10 degrees F. colder is not ofconsequence, so long as a sufficient differential exists to facilitatethe recording of the temperature anomaly produced by entry of the fluidinto the particular strata or zone of the well bore. The temperature ofthe treating fluid is altered prior to pumping the treating fluid intothe well so that the significant differential will exist. This may bedone by either heating or cooling the treating fluid prior to theintroduction of the same into the well. It is usually easier and quickerto heat fluid than to cool it; and, therefore, most treating operationsrequiring a change of fluid temperature are carried out by using a fluidhotter than the bottom hole temperature. This may be effected in theusual manner by a hot oil truck or a steamer truck being used to heatthe fluids introduced into the well. After the treating fluid has beenpumped into the well and displaced by pressure into the formation in theusual manner of treating wells, the temperature logging tool is run intothe well bore and the record of the temperature gradient and thetemperature differential curves obtained, following such treatment, andcompared to the base log previously taken.

As schematically shown in FIGURE 2, the treating fluid has entered thesecond zone 22 which is shown hatched vertically, and, as a result, thetemperature gradient curve 50 at that zone or that depth in the wellshows a decrease in temperature at 51 at that level in the well bore.Also, the temperature dilferential curve 60 shows a sharp change 61 atthat level, indicating that the treating fluid has entered the secondzone 22. Several logging runs are usually made, and each is carefullyinspected for new anomalies over the base log, or for the decay rate ofprevious anomalies. Ghost anomalies, resulting from washouts, cavitiesin the bore hole, or the like, may also appear on the logs. From thelogs so obtained, and schematically illustrated generally in FIGURE 2,the operator can determine that zone 22 has been treated. Also, thesubstantial extent of a zone is obtained from the drillers log of thewell and from other types of logs of the well previously taken, and withthe information obtained from the temperature log and available from theprevious logs, the operator then determines the volume or size of thediversion material or blocking material charge or plug to be pumped intothe well prior to the second stimulation stage. Such diversion materialmay be one or more of a number of materials, commonly, however, salt,moth balls or the like, carried in a concentration of gels forsupporting and carrying the blocking or diverting material. Thediverting material may be salt, paraffin beads, silicon compounds orsand, various napthalenes, walnut shells, natural or crushed, leatherparticles, oyster shells, limestone, aromatic resins, acetate film,rubber, or ball sealers of rubber, nylon or other synthetics suitablefor the purpose. The particle shapes will vary from angular to sphericaland may be regular or irregular in configuration. Various solvents areused for each to assure removal of the blocking agent after treatment,which may be water, hydrocarbons, acids, hydroxides, or the like. Thetemporary gels used for supporting the blocking agents may be emulsifiedacid, thickened water, or similar materials commonly in use fortemporary gels. Permanent gels may include thickened water, silicategels, cement slurries or the like.

The calculated volume of diverting material or blocking material is thenpumped into the well bore, immediately followed by the next stimulationcharge. The stimulation charges used may include thickened hydrocarbon,in situ gels consisting of oil, fatty acid caustic, refined oil, whichmay be refinery residuals, or native lease crude oils or crudes,thickened water, unaltered water, thickened acids, emulsified orunaltered, acid solutions, corrosion inhibitor additive may be included,scale inhibitor additives may be included, surfactants may be added, asmay bactericides, cleaning solutions, conversion solutions, or heatgeneration materials such as magnesium or the like and muriatic, nitric,or other acid. In addition, a proppant may be incorporated in thetreating fluid, to assure that the fractured formation or openedformation remains in an open condition. Such proppants may include sand,walnut hulls, glass beads, aluminum pellets, iron shot, plastic pellets,or the like. It is obvious that the proppants may form a part of theblocking agent. However, it is desired that a removable blocking agentform a major part of the diversion material. It is for this reason thatsalt, or a naphthalene such as moth balls or the like, is commonly usedto form a major portion of the blocking material in most cases. As aresult of the use of such blocking agents, the aqueous fluids present inthe well bore will dissolve the salt, or the liquid hydrocarbons presentin the well bore or which may be introduced into the well bore as aportion of the treating fluid, will remove a major part of the blockingagent to permit the formation to produce. This removal of the blockingagent, however, is not accomplished until after all zones have beentreated.

Following the injection of the diversion or blocking plug and the secondstimulation stage, one or more temperature logs are run. A schematicillustration of the Well in which the second step has been effected isillustrated in FIGURE 3 Where the third zone 23 is indicated "byvertical cross-hatching to have been treated. The temperature logfollowing such treatment is illustrated to the right of the schematicwell bore illustration, and the temperature gradient curve 50 shows areduction in the deviation or anomaly at 51 adjacent the second zone 22,but shows a sharp deviation or anomaly 52 adjacent the third zone 23.Likewise, the temperature differential curve still shows a slightdeviation 61 adjacent the upper edge of the second zone 22, but shows asharp deviation or anomaly 62 adjacent the third zone 23. The deviationsto the right on the differential curve result from increases in thetemperature at the slate or shale strata between the porous formations.

From the information available as a result of the temperature log andfrom the previous logs of the well, the operator determines the size ofthe diversion charge or plug to be used for closing off or blocking thethird formation 23 prior to injection of a third stimulation stage. Thediversion or blocking plug is then prepared and pumped into the wellbore, immediately followed by the third stimulation or treating stage.

Following the treatment of the well with the third stimulation stage afourth series of temperature logs are taken and the logs compared withthe previous logs. As shown in FIGURE 4, the temperature gradient log 50shows an anomaly 53 adjacent the upper or first zone 21, indicating thatthe treating fluid has entered such upper zone. It will also be seenthat the anomaly 52 adjacent the third zone 23 shows a temperature decayas compared to the deviation at that point shown in FIGURE 3. Thisindicates that no treating fluid has entered the third zone during thisstage. The temperature diflerential log 60 also shows a sharp deviationor anomaly 63 adjacent the upper edge of the upper zone 21, and likewiseshows decreases or decays in the anomalies existent adjacent thepreviously treated zones. This record clearly indicates that the upperzone 21 was treated by such third stage. From the information availablefrom the logs, the proper blocking or diverting plug is calculated toseal olf the upper zone 21, and the diversion plug is then pumped intothe well bore in the manner previously set forth, followed by the nextstimulation stage. Following such treatment, the tempera ture logs aretaken and the schematic illustration in FIGURE 5 indicates that thelower or fourth zone 24 has been treated. The temperature gradient curveshows a sharp anomaly 54 adjacent the lower Zone 24, and similarly showsa decay of the anomalies 51, 52, and 53 when compared with the previouslogs of FIGURES 2, 3 and 4. In addition, the temperature differentialcurve 60 shows a sharp anomaly 64 adjacent the lower zone 24, andlikewise shows a decay in the anomalies previously noted. It is alsoindicated at the lower end of the curves that the temperature has risensubstantially below the lower zone. This log indicates that all fourzones previously known to be present in the well have been successfullytreated.

It is believed readily apparent that the several steps outlined may bealtered or adjusted, depending upon the interpreted results of thedown-hole temperature logging. The various stages may be increased,decreased, or eliminated, as determined desirable from the down-holeconditions indicated by the logs.

It is also believed readily apparent that a producing or injection wellin which only certain zones are desired to be treated, it is notnecessary that the treating fluid be pumped into the well. Instead,after the base log has been run, a dummy fluid, which may not be astimulation fluid, but a fluid used simply to indicate or locate thezone accepting the fluid, is pumped into the Well. The steps previouslyoutlined for treatment of the several zones of the well are thenfollowed until it has been indicated that the zone which it is desiredto treat shows on the temperature log to be accepting the dummy fluid bythe temperature anomaly appearing on the logs adjacent that formation.At this point, a stimulation stage of treating fluids is injected intothe well without previously injecting the diverting or blocking plug orcharge so that the treating fluid is thus inserted or injected into onlythe zone desired to be treated. In cases where there are other zones inwhich treatment is desired, the process may be continued until all suchzones have been treated.

In certain wells in which some of the zones have been previously treatedand require no further treatment, there may be a selected zone which itmay be desired be treated. The process just described, using the dummyfluids to determine the point at which the zone to be treated isaccepting fluid is followed, and at that point the desired zone is thentreated with the desired treating fluid or stimulation stage.

It is also believed readily apparent tht only certain zones may bedesired to be treated in the well and the procedure outlined hereinabovemay be followed for that purpose. The location of channels,communication between zones or thief zones may be determined byfollowing basically the procedure outlined hereinabove. Also, Zones tobe treated may be defined before treatment by following the procedureoutlined utilizing the dummy fluids previous to inserting the treatingfluid. In addition, a permanent seal of a zone may be affected byfollowing the procedure ontlined, utilizing dummy fluids and blocking ordiversion fluids, except that when the zone to be treated is determinedto be accepting fluid, a permanent sealant may then be inserted intosuch zone.

It is also readily apparent that the diverting fluid may include aproppant for maintaining the blocked-off or closed-off zone in an opencondition after the diverting materials have ben moved from the zone bysolution, washing, or the natural flow of fluids from the well, or thelike. It is also readily apparent that where wells have been deepened,and it is not desired to treat the older portion of the well bore, theprocess outlined utilizing the dummy fluids may be followed to seal offthe old previously treated zones and to treat only the desired zones.

It is believed readily apparent that the method of this inventionprovides for accurate, selective treatment of well formations, thatcontrol of the use of diverting or blocking material, as well astreating materials, may be accurately computed and result in a moreeconomical treatment of the wells, eliminating re-treatment necessaryunder the continuous process or other processes. It is also believedthat it is apparent that zones which could not be treated by the otherprocesses may be treated utilizing this process. Also, it is readilyapparent that this method results in complete treatment of the severalzones present in the Well bore and an accurate determination that allsuch zones have been successfully treated. The process permitsevaluation of all zones treated; provides for accurate calculation andintroduction of diverting agents after each treating stage; permitsimmediate recognition of any communicating or channelling problem orirregular existing downhole conditions in the well bore; assures thatall productive intervals are stimulated for improved, sustained futureproduction. Actual tests have indicated that wells previously treated bythe commonly used methods, which have been subsequently treated by thismethod, have resulted in increases of production of flow of fluid of theorder of four to five times or more over the previ- OUs production.

It will therefore be seen that all the objects desired have beenaccomplished as described.

The foregoing description of the invention is explanatory only andchanges in the procedures used, the materials used and the steps of themethod followed, may be made by those skilled in the art within thescope of the appended claims Without departing from the spirit of theinvention.

What is desired to be secured by Letters Patent is:

1. A method of treating a well drilled into earth strata comprising:making a temperature survey of the well bore to establish a base curveof temperature gradient and temperature differential in the well bore;treating the earth strata in said well bore; making a temperature surveyof the well bore following such treatment; determining the stratatreated; selectively treating another strata area in said well boreother than the strata area previously treated; and making a temperaturesurvey to determine that the desired strata area has been treated.

2. The method of claim 1 wherein the treating is effected by introducinginto the well bore fluid altered to a temperature differing from theambient formation tem perature in the earth strata being treated.

3. A method of treating a well drilled into earth strata comprising:making a temperature survey of the well bore to establish a base curveof temperature gradient and temperature differential in the well bore;inserting a treating fluid charge into the well bore to treat the earthstrata therein; making a temperature survey of the well bore followingsuch treatment to determine the strata area treated; blocking off thearea first treated and inserting a second treating fluid charge into thewell following such blocking; making a temperature survey of the wellbore following insertion of such second treating fluid charge anddetermining the well strata treated by such second charge; thenrepeating the blocking, treating and surveying steps of the process asdesired until all desired strata in the well have been treated.

4. A method of treating a well as set forth in claim 3 wherein thetemperature of the treating fluid inserted into the well bore differsfrom the temperature of the earth strata being treated, whereby entry ofthe treating fluid into the treated earth creates a temperaturedifferential at such point detectable by said temperature survey.

5. A method of treating wells as set forth in claim 4 wherein thetemperature of the treating fluid is altered at the surface preparatoryto insertion into the well.

6. A method of treating wells as set forth in claim 4 wherein thetreating fluid is heated at the surface to a value above the highestambient formation temperature in the earth strata being treated.

7. A method as set forth in claim 3 wherein the blocking of the treatedareas is effected by means of a diverting blocking agent closing offentry of treating fluid to such zone, such diverting blocking materialbeing inserted into the well bore prior to the treating fluid charge.

8. A method of treating a well of the character set forth in claim 3wherein the blocking off of the treated area is effected by means of adiverting blocking material having a proppant forming a part thereof.

9. A method of the character set forth in claim 8 wherein the divertingblocking material comprises one or more of the group consisting of salt,wax paraffin, silicon compounds, naphthalene compounds, nut shells,leather particles, oyster shells, lime stone, aromatic resin, acetatefilm, natural or synthetic rubber, and ball sealers of rubber, rubbercoated nylon or similar plastics.

10. A method of treating a well as set forth in claim 8 wherein theproppant forming a part of the diverting blocking material consists ofone or more of the group including sand, nut hulls, glass beads,aluminum pellets, iron shot.

11. A method of treating a well drilled into earth strata comprising:making a temperature survey of the well bore to establish a base curveof temperature gradient and temperature differential in the well bore;treating the earth strata in said Well bore; making a temperature surveyof the well bore following such treatment to determine the strata areatreated; again treating and controlling treatment of the earth strata totreat a strata area in said well bore other than the strata areapreviously treated; and making a temperature survey to determine thatthe desired strata area has been treated.

12. A method of treating a well drilled into earth strata having aplurality of separate formations, said method comprising: making atemperature survey of the well bore to establish a base curve oftemperature gradient and temperature differential in the well bore;introducing a treating fluid into the Well bore to treat the earthstrata in said well bore; making a temperature survey of the well borefollowing such treatment to determine the formation treated; selectivelytreating the several formations in the well in successive treatments toselectively successively treat a formation other than the formationpreviously treated; making a temperature survey of the well borefollowing each such treatment to determine that the desired formationhas been treated; and repeating the steps of selective treatment andsurveying until all desired formations in the well have been treated.

13. A method of treating a well drilled into earth strata comprising:making a temperature survey of the well bore to establish a base curveof temperature gradient and temperature differential in the well bore;treating the earth strata in said well bore; making a temerature surveyof the well bore following such treatment to determine the stratatreated; selectively treating another strata in the well bore other thanthe strata previously treated; making a temperature survey to determinethat the desired strata has been treated; and repeating selectivetreatment of the several strata in the well in successive treatments;and determining by temerature survey that the desired strata has beentreated following each treatment.

14. A method of treating a well drilled into earth strata comprising:making a temperature survey of the well bore to establish a base curveof temperature gradient and temperature differential in the well bore;inserting a treating fluid charge into the well bore at a temperaturediffering from the ambient temperature of the earth strata to treat theearth strata therein; making a temperature survey of the Well borefollowing such treatment to determine the strata area treated; insertinga second treating fluid charge into the well bore at a temperaturediffering from the ambient earth strata temperature to treat anotherearth strata area than the strata area previously treated; making atemperature survey of the earth strata following insertion of suchsecond treating fluid charge to determine that the desired earth strataarea has been treated by said second charge.

15. A method of treating a well as set forth in claim 14 wherein thetreating fluid charge inserted into the Well comprises an acidizingfluid or hydraulic fracturing fluid to induce improved flow of fluids inthe formation into and out of the well bore, or both.

16. A method of treating a well as set forth in claim 14 wherein thetreating fluid charges inserted into the well are heated at the surfaceto a value above the highest ambient earth strata temperature in thestrata being treated.

17. A method of treating a well as set forth in claim 14 wherein thetreating fluid charges inserted into the well are cooled at the surfaceto a value below the lowest ambient earth strata temperature in thestrata being treated.

18. A method of treating a well as set forth in claim 14, and theadditional steps of: inserting successive treating fluid charges intothe well bore at a temperature differing from the ambient temperature ofthe earth strata being treated to successively selectively treat anotherearth strata area than the strata areas previously treated; and making atemperature survey of the earth strata following each successiveinsertion of treating fluid to determine that the desired earth strataarea has been treated by successive treating fluid charges.

References Cited UNITED STATES PATENTS 5 8/1936 Schlumberger 1665 5/1941Leonardon 73154 7/1942 Schlumberger 73154 8/ 1945 Abadie. 1O

4/1954 Basham 73154 X 8/1957 Nowak 1664 X 10 3,122,016 2/1964 Fordham73-154 3,410,136 11/1968 Johns et a1. 73-154 OTHER REFERENCES Frick eta1.: Petroleum Production Handbook, vol. II, Reservoir Engineering,McGraw-Hill Book Co., Inc., New York, NY. (1962) (pp. 4523 to 4525relied on).

STEPHEN I. NOVOSAD, Primary Examiner US. Cl. X.R.

